Effects of cadmium and nickel interaction on growth and some physio-biochemical indices of Calotropis procera (Aiton) W.T.Aiton

Calotropis procera (Aiton) W.T.Aiton is a xerophytic perennial shrub that grows in tropical regions. Potentially toxic trace elements are environmental pollutants and a severe problem for ecological, nutritional, and environmental reasons. The aim of this study was to investigate the effects of different concentrations of nickel (NiSO₄) and cadmium (CdSO₄) on the physio-biochemical indices and growth parameters of Calotropis procera. The seeds were cultivated in perlite, and then seedlings were treated by nickel and cadmium concentrations for three weeks. The results showed that cadmium and nickel interactions significantly affected the growth and physio-biochemical indices of Calotropis procera. Nickel and cadmium concentrations increased in the shoots and roots as the external concentrations were raised. The highest amounts of nickel were detected in the shoots and roots as 229.00 ± 4.61 and 275.00 ± 10.40 mg kg⁻¹ dry weight, respectively. Also, the highest amounts of cadmium in the roots and shoots were respectively measured as 376.54 ± 4.01 and 49.50 ± 4.76 mg kg⁻¹ dry weight. Increasing nickel and cadmium levels caused decreases in root and shoot length, root and shoot dry weights, photosynthetic pigments, and total protein content. In contrast, carbohydrate and proline concentrations increased with higher nickel and cadmium levels, likely as a defense mechanism. These findings suggest that Calotropis procera has the potential to phytostabilize cadmium in contaminated soils.